Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability (CVE-2025-6543)
Severity: critical · Patch status: unknown · Since 2025-06-30 · CVE-2025-6543
Citrix NetScaler ADC and Gateway contain a buffer overflow vulnerability leading to unintended control flow and Denial of Service. NetScaler must be configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server. CISA added CVE-2025-6543 to its Known Exploited Vulnerabilities catalog on Jun 30, 2025, which means attackers are exploiting it in the wild.
What to do
- Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- US federal agencies must remediate by Jul 21, 2025 (BOD 22-01); treat that as the outer limit.
Sources
All live incidents on Threat Watch
